title: DNA damage and cell cycle arrest induced by protoporphyrin IX in sarcoma 180 cells.
abstract: BACKGROUND
  Porphyrin derivatives have been widely used in photodynamic therapy as effective sensitizers. Protoporphyrin IX (PpIX), a well-known hematoporphyrin derivative component, shows great potential to enhance light induced tumor cell damage. However, PpIX alone could also exert anti-tumor effects. The mechanisms underlying those direct effects are incompletely understood. This study thus investigated the putative mechanisms underlying the anti-tumor effects of PpIX on sarcoma 180 (S180) cells.
  
  
  METHODS
  S180 cells were treated with different concentrations of PpIX. Following the treatment, cell viability was evaluated by the 3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT) assay; Disruption of mitochondrial membrane potential was measured by flow cytometry; The trans-location of apoptosis inducer factor (AIF) from mitochondria to nucleus was visualized by confocal laser scanning microscopy; DNA damage was detected by single cell gel electrophoresis; Cell cycle distribution was analyzed by DNA content with flow cytometry; Cell cycle associated proteins were detected by western blotting.
  
  
  RESULTS
  PpIX (≥ 1 µg/ml) significantly inhibited proliferation and reduced viability of S180 cells in a dose-dependent manner. PpIX rapidly and significantly triggered mitochondrial membrane depolarization, AIF (apoptosis inducer factor) translocation from mitochondria to nucleus and DNA damage, effects partially relieved by the specific inhibitor of MPTP (mitochondrial permeability transition pore). Furthermore, S phase arrest and upregulation of the related proteins of P53 and P21 were observed following 12 and 24 h PpIX exposure.
  
  
  CONCLUSIONS
  PpIX could inhibit tumor cell proliferation by induction of DNA damage and cell cycle arrest in the S phase.
authors.affiliation: Key Laboratory of Medicinal Resources and Natural Pharmaceutical Chemistry, Ministry of Education, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Wang
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Li
authors.forename: Quanhong
authors.initials: Q
authors.lastname: Liu
authors.forename: Pan
authors.initials: P
authors.lastname: Wang
mesh_terms: D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D017319:Photosensitizing Agents / Q000494:pharmacology* / Q000627:therapeutic use; D011524:Protoporphyrins / Q000494:pharmacology* / Q000627:therapeutic use; D059807:S Phase Cell Cycle Checkpoints / Q000187:drug effects*; D012510:Sarcoma 180 / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D051033:Apoptosis Inducing Factor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D016159:Tumor Suppressor Protein p53; C028025:protoporphyrin IX